1. Field of the Invention
This invention relates to hybrid motor vehicles and methods for their control.
2. Description of the Related Art
Hybrid vehicle powertrains are being studied as a way to improve the fuel efficiency of motor vehicles. Commonly-assigned U.S. Pat. No. 6,719,080 (“Hydraulic Hybrid Vehicle”) to Gray, and commonly assigned U.S. patent application Ser. No. 13/415,109 (“Modular Hydraulic Hybrid Drivetrain”), filed Mar. 8, 2012, which are both incorporated herein by reference, describe two examples of a hydraulic hybrid powertrain for a motor vehicle utilizing a series mode of operation. The series mode of operation on a hydraulic hybrid vehicle includes an engine-driven hydraulic pump which receives working fluid from a low pressure fluid source and pressurizes the fluid to a higher pressure. A high pressure fluid line (or other fluid connection) conveys the pressurized fluid to a hydraulic motor, where the pressurized fluid drives the hydraulic motor to provide useful work. An energy storage high pressure accumulator is fluidly connected to the high pressure fluid line, to (1) receive pressurized fluid from the hydraulic pump and retain the fluid in a highly pressurized state for energy storage purposes, and (2) provide pressurized fluid as needed to drive the hydraulic motor. Hybrid electric vehicle powertrains are also well-known in the art.
Efficiency and performance of hybrid motor vehicles are highly dependent on selection of effective vehicle control methods for governing the actions and interactions of the hybrid powertrain components (e.g., engine, pump, motors, valves, accumulators, and auxiliary systems for a hydraulic hybrid) within the vehicle. There is a need for continued improvements in vehicle control methods, to further improve the efficiency and performance of hybrid motor vehicles. Optimum vehicle controls for a hybrid vehicle can be significantly affected by factors such as vehicle weight and drive cycles. It is therefore beneficial to facilitate vehicle control adjustments responsive to such factors.